Odorant binding proteins play a key role in the olfactory system and are involved in the odor perception and discrimination of insects. To investigate the potential physiological functions of SaveOBP9 in Sitobion avenae, fluorescence ligand binding experiments, molecular docking, RNA interference, and behavioral tests were performed. Fluorescence binding assay results showed that SaveOBP9 had broad and high (Ki < 10 μM) binding abilities with most of the wheat volatiles, but was more obvious at pH 7.4 than pH 5.0. The binding sites of SaveOBP9 to the volatiles were predicted well by three-dimensional docking structure modeling and molecular docking. Moreover, S. avenae showed a strong behavioral response with the four compounds of wheat. The reduction in mRNA transcript levels after the RNA interference significantly reduced the expression level of SaveOBP9 and induced the non-significant response of S. avenae to the tetradecane, octanal, decanal, and hexadecane. This study provides evidence that SaveOBP9 might be involved in the chemoreception of wheat volatile organic compounds and can successfully contribute in the integrated management programs of S. avenae.

Chemosensory proteins (CSPs) play important roles in insects' chemoreception, although their specific functional roles have not been fully elucidated. In this study, we conducted the developmental expression patterns and competitive binding assay as well as knock-down assay by RNA interference both in vitro and in vivo to reveal the function of NlugCSP10 from the brown planthopper (BPH), Nilaparvata lugens (Stål), a major pest in rice plants. The results showed that NlugCSP10 messenger RNA was significantly higher in males than in females and correlated to gender, development and wing forms. The fluorescence binding assays revealed that NlugCSP10 exhibited the highest binding affinity with cis-3-hexenyl acetate, eicosane, and (+)-β-pinene. Behavioral assay revealed that eicosane displayed attractant activity, while cis-3-hexenyl acetate, similar to (+)-β-pinene significantly repelled N. lugens adults. Silencing of NlugCSP10, which is responsible for cis-3-hexenyl acetate binding, significantly disrupted cis-3-hexenyl acetate communication. Overall, findings of the present study showed that NlugCSP10 could selectively interrelate with numerous volatiles emitted from host plants and these ligands could be designated to develop slow-release mediators that attract/repel N. lugens and subsequently improve the exploration of plans to control this insect pest.